There are two basic ways that ocean tides are used to generate electricity: tidal streams and tidal barrages. There has been a great deal of recent interest in tidal stream power, which works like wind power driven by underwater tidal currents. But tidal barrages or barriers are an older technology that is the basis of the largest tidal power installations in the world.
The basic principle resembles a hydroelectric dam. A barrage or barrier closes off an inlet of the ocean and gates allow water to enter when the tide rises. When the tide falls, the difference in water levels is used to drive turbines that generate electricity.
The 240-megawatt tidal plant in the La Rance estuary in France was commissioned in 1966 and is still the second largest installation in the world. The largest tidal barrage plant, located in South Korea, was commissioned in 2012 and produces 254 megawatts.
These large tidal plants are only practical in locations that have large tidal ranges. However, there are quite a few such places around the world. A particularly attractive feature of tidal barrage energy plants is that their output is completely predictable. We know the behavior of the tides quite well.
Several even larger plants are being proposed in South Korea and a 240-megawatt tidal lagoon –basically a circular dam in the ocean – is under development in Wales. These large tidal power plants can provide a very significant contribution to our electricity needs by making use of a free, clean and reliable source of energy.
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Turning the Tide on Barrage Technology
Photo, taken October 10, 2008, courtesy of David Stanley via Flickr.
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Earth Wise is a production of WAMC Northeast Public Radio. Support for Earth Wise comes from the Cary Institute of Ecosystem Studies in Millbrook, NY.